WEDNESDAY, Jan. 9 (HealthDay News) -- It may be possible to predict who will develop psychotic illnesses, such as schizophrenia and bipolar disorder, very early in the disease process, a new study says.

The study found five factors that were often present prior to the diagnosis of a psychotic disorder in children who were already at high risk of such disorders. When three or more of these factors were present, the study found an 80 percent likelihood of developing psychosis within two and a half years.

"Not everybody who has early symptoms goes on to develop psychosis. But if we identify the group in which 80 percent will develop psychosis, the efforts of intervention would be best applied to those at highest risk," said study author Tyrone D. Cannon, the Staglin Family professor of psychology, psychiatry and biobehavioral sciences at the University of California, Los Angeles.

Results of the study were published in the Jan. 7 issue of the Archives of General Psychiatry.

Cannon said it's not yet known if early intervention with anti-psychotic medications would help prevent the development of psychotic illnesses. He said two studies have suggested that early psychological intervention might be more useful, because they can give teens skills for staying connected, solving problems and for conflict resolution.

Symptoms of psychosis are seen in numerous mental health disorders, such as bipolar disorder, schizophrenia, depression, and with some forms of alcohol or drug abuse, according to the American Academy of Child and Adolescent Psychiatry (AACAP). The two most common psychotic symptoms are delusions and hallucinations, according to AACAP. Delusions are false but firmly held beliefs. Hallucinations are false sensory perceptions, such as hearing voices when no one is talking.

While these symptoms can certainly be disturbing, Cannon said, "most people with psychotic disorders aren't really more prone to violence." And, he added, this study wasn't designed to address violence or the potential for violence in those with psychotic illness, so it isn't clear if earlier identification and intervention for these illnesses could help prevent incidents like school shootings.

Cannon and his colleagues prospectively studied 291 young people who sought mental health treatment at one of eight different treatment centers in North America. The average age of the study participants was 18 years, and all sought treatment for early symptoms of psychosis, such as unusual thoughts.

During the two-and-a-half-year follow-up, 35 percent of this group went on to develop psychotic illness.

The researchers identified five factors that could help predict the eventual development of psychosis. These included a family history of schizophrenia with recent deterioration in functioning; higher levels of unusual thoughts; higher levels of suspicion or paranoia; greater social impairment; and a history of substance abuse.

When two or three of these factors were present, the odds of psychotic illness jumped. Two factors increased the likelihood of psychotic illness to 68 percent, and three factors combined raised the risk to 80 percent.

"This was a really good study in terms of size, and once it's replicated can add on to the field," said Dr. Christopher Lucas, an associate professor of child and adolescent psychiatry at the New York University School of Medicine and the director of the Early Childhood Service at the New York University Child Study Center.

But, the question is, Lucas added, "If you have somebody with this picture, do you treat them prophylactically?"

Both Lucas and Cannon noted that this study was done on a high-risk population, so it can't be generalized for the whole population.

Parents need to be on the lookout for a child who withdraws socially and stops participating in activities he or she once enjoyed, according to Cannon. He said it's not usually until a child is receiving mental health treatment that they admit to having delusions or hearing voices or feeling a greater sense of suspicion, so parents might not notice such symptoms. Parents should be especially wary of any of these symptoms if there's a family history of psychotic illnesses, according to the study.

SOURCES: Tyrone Cannon, Ph.D., Staglin Family professor of psychology, psychiatry and biobehavioral sciences, associate director, Semel Institute of Neuroscience and Human Behavior, and director, Center for Cognitive Neuroscience, University of California, Los Angeles; Christopher P. Lucas, M.D., M.P.H., associate professor, child and adolescent psychiatry, New York University School of Medicine, and director, Early Childhood Service, New York University Child Study Center, New York City; Jan. 7, 2008, Archives of General Psychiatry